INSERT from JOIN inserts null values - sql

Question

The need to insert values from 3 tables into another table called myTable. The required fields in myTable are:
[Id_student] int,
[id_subjects] int
[degrees] float
[st_Name] nvarchar(30)
[Id_Class] int
[Id_Group] int
[Class] nvarchar(15)
[group] nvarchar(15))` ..
I created the stored procedure below. But after viewing the table I found that only the passed parameters were saved! ie #Id_student , #id_subjects , #degrees. Can anyone explain what is wrong with this code?
CREATE storedprocedure mySp_myTable_insert
#Id_student int,
#id_subjects int,
#degrees int
as
DECLARE #st_Name nvarchar(30)
SELECT #st_Name = pst.st_Name FROM dbo.sudents AS pst where pst.id_student=#id_student ;
INSERT [myTable]
(
[Id_student],
[id_subjects],
[degrees],
[st_Name],
[Id_Class],
[Id_Group],
[Class],
[group]
)
(select
#Id_student,
#id_subjects,
#degrees,
#st_Name
,tc.Id_Class
,tg.Id_Group
,tc.Class
,tg.group
from dbo.subjects sbj
inner join tGroup tg
inner join tClass tc
on tc.Id_Class=tg.Id_Class
on sbj.Id_Group =tg.Id_Group
where sbj.id_subjects=#id_subjects)

Answer 1

I think you should drop the parentheses around the SELECT statement and fix the order of the join-on keywords/clauses.
Try this version:
CREATE storedprocedure mySp_myTable_insert
#Id_student int,
#id_subjects int,
#degrees int
as
DECLARE #st_Name nvarchar(30)
SELECT #st_Name = pst.st_Name FROM dbo.sudents AS pst where pst.id_student=#id_student ;
INSERT [myTable]
(
[Id_student],
[id_subjects],
[degrees],
[st_Name],
[Id_Class],
[Id_Group],
[Class],
[group]
)
select
#Id_student,
#id_subjects,
#degrees,
#st_Name
,tc.Id_Class
,tg.Id_Group
,tc.Class
,tg.group
from dbo.subjects sbj
inner join tGroup tg on sbj.Id_Group =tg.Id_Group
inner join tClass tc on tc.Id_Class=tg.Id_Class
where sbj.id_subjects=#id_subjects
GO